Ellen, one word that Steve: should have added to "fast" and "efficient" is dangerous. Sandblasting will generate a tremendous amount of dust, of which a significant part will be from the paint. This old paint probably has a lot of red lead in it. While a contractor should take a lot of time to be sure that the dust is contained and removed, they will not get it all. I suggest that you look at a chemical stripper like Peel Away. This will have an element of risk as well as be messy also. My opinion is that the Peel Away represents hazards that are basically more forseeable and controllable.
As usual, there can be at least 2 good answers to many questions. Steve: and I differ on many issues like painting brick to begin with and metal studs versus steel studs. To questions like these, there really is no "right" answer to every situation. But I do think that you should consider Peel Away as a viable alternate. You can get more info at www.PeelAway.com.